Pagurixus rubrovittatus, Komai, 2010

Komai, Tomoyuki, 2010, New species and new records of the hermit crab genus Pagurixus Melin, 1939 (Crustacea: Decapoda: Anomura: Paguridae) from the Indo-West Pacific, Journal of Natural History 44 (21 - 22), pp. 1269-1342 : 1321-1328

Pagurixus rubrovittatus sp. nov.

( Figures 23–25 )

Material examined

Holotype. SURPRISES, stn CP 1376, Surprise Atoll , New Caledonia, 18°27.2′S, 163°09.2′E, 39 m, 9 May 1999, male SL 4.4 mm (MNHN-Pg 8325).

Paratypes. New Caledonia. LAGON NORD, stn 458, Surprise Atoll , 18°27′S, 163°02′E, 40 m, 1 March 1985, 1 male SL 2.9 mm (MNHN-Pg 8326); stn 483, 19°01′S, 163°32′E, 33 m, 2 March 1985, 1 male SL 3.0 mm (MNHN-Pg 8327); stn 521, 19°05′S, 163°38′E, 39 m, 5 March 1985, 1 female SL 3.2 mm (MNHN-Pg 8328) . LAGON EST, stn 639, E of Lagon, 21°55.5′S, 166°44.1′E, 48–50 m, 7 August 1986, 1 female SL 3.4 mm, 1 ovigerous female SL 3.5 mm (MNHN-Pg 8329); stn 642, E of Lagon, 21°54.2′S, 166°42.2′E, 47– 44 m, 7 August 1986, 1 ovigerous female SL 2.9 mm (MNHN-Pg 8330); stn 651, 21°48.0′S, 166°36.4′E, 48 m, 7 August 1986, 1 male SL 2.8 mm (MNHN-Pg 8331); stn 663, E of Lagon, 21°42.2′S, 166°30.5′E, 38–40 m, 8 August 1986, 1 male SL 4.5 mm, 1 female SL 4.8 mm (MNHN-Pg 8332); stn 664, 21°43.9′S, 166°29.4′E, 28–30 m, 8 August 1986, 1 ovigerous female SL 3.3 mm (MNHN-Pg 8333); stn 729, E of Lagon, 21°18.7′S, 165°53.5′E, 42–45 m, 12 August 1986, 1 male SL 3.5 mm (MNHN-Pg 8334); stn 732, E of Lagon, 21°18.9′S, 165°50.9′E, 43–50 m, 12 August 1986, 1 male 4.0 mm (MNHN-Pg 8335). Stn DW 1236, Lagon , 21°18.13′S, 165°53.68′E, 45 m, 13 March 1993, 2 males SL 2.4, 4.6 mm (MNHN-Pg). SURPRISES, stn DW 1388, 18°23.8′S, 163°06.9′E, 40 m, 11 May 1999, 1 ovigerous female SL 4.1 mm (MNHN-Pg); stn DW 1397, 18°21.9′S, 163°03.9′E, 43 m, 13 May 1999, 1 male SL 1.9 mm (MNHN-Pg). Chesterfield Islands. CORAIL 2, stn DW 58, 19°18.38′S, 158°33.57′E, 58– 50 m, 23 July 1988, 1 male SL 4.9 mm (MNHN-Pg 8339) .

Description

Shield ( Figure 23A ) about 1.1 times as long as broad; anterior margin between rostrum and lateral projections concave; anterolateral margins terraced; dorsal surface slightly convex, with paired tufts of stiff setae surrounding gastric region. Rostrum triangular, distinctly overreaching lateral projections. Lateral projections triangular, weakly produced, usually with small submarginal spine.

Ocular peduncles ( Figure 23A ) moderately long, stout, 0.6–0.7 length of shield, with row of tufts of short setae on dorsal surface mesially; cornea somewhat dilated, corneal width 0.4–0.5 of peduncular length; basal part slightly inflated, but distinctly narrower than corneal width. Ocular acicles subovate or subtriangular, each with very small submarginal spine.

Antennular peduncles ( Figure 23A ) reaching or slightly overreaching distal corneal margins. Ultimate segment with single relatively short seta at dorsolateral distal angle; ventral surface naked. Basal segment with tiny lateral spine on statocyst lobe ( Figure 22B ). Ventral flagellum ( Figure 22B ) with row of numerous moderately short setae on each lateral and mesial margin; first article with numerous thin setae on ventral surface.

Antennal peduncles ( Figure 23A ) overreaching distal corneal margins by 0.3–0.5 length of fifth segments. Third segment with few tufts of stiff setae on mesial surface, but unarmed. Second segment with tiny spine at dorsomesial distal angle; laterodistal projection not reaching midlength of fourth segment, terminating in simple or bifid spine. Antennal acicle moderately long, reaching nearly to distal corneal margin; mesial margin with row of tufts of short to moderately long, stiff setae. Antennal flagellum moderately long, about 4.0 times of shield length.

Male right cheliped ( Figures 24A–F , 25A, B ) unusually elongate. Chela 4.3 times longer than wide at most. Dactylus about 0.4 length of palm, weakly curved ventrally, terminating in calcareous claw; dorsomesial margin not delimited; surfaces finely granular, ventral surface with several tufts of long setae; cutting edge with one obtuse tooth proximal to midlength. Palm subrectangularly lengthened, slightly longer than carpus; convex dorsal surface finely granular, dorsolateral and dorsomesial margins not delimited; lateral, mesial and ventral surfaces also finely granular, with scattered tufts of long setae on ventral surface distally. Fixed finger terminating in calcareous claw, with low convexity at about middle of cutting edge. Carpus elongate, length about 3.3 of distal width, subequal in length to merus; dorsomesial and dorsolateral margins not clearly delimited, with one small spine arising from midlength of dorsomesial margin; dorsal surface with covering of sharp granules; lateral surface finely granular, with trace of dorsolateral ridge; mesial and ventral surfaces finely granular. Meral–carpal articulation with about 45° of clockwise rotation; dorsal surface of merus with covering of granules, occasionally forming transverse rows, dorsodistal margin with row of five small spines; lateral face covered with coarse granules, ventrolateral margin with four closely-spaced small spines distally followed by small sharp granules; mesial face also coarsely granular, ventromesial margin one small tooth at ventrodistal angle and row of sharp granules; ventral surface weakly convex, covered with coarse granules. Ischium with smooth ventromesial margin; ventral surface granular.

Female right cheliped ( Figures 24E, F , 25C ) subequal in length and generally similar to left cheliped. Chela elongate, subovate in dorsal view, about 3.1 times longer than broad. Dactylus slightly longer than palm; dorsomesial margin not delimited; surfaces with tufts of stiff setae; cutting edge with row of small corneous teeth in distal half, terminating in small corneous claw. Palm about half length of carpus; dorsal surface slightly convex, with minute tubercles and few short setae; dorsolateral margin delimited by row of tiny tubercles or granules nearly to tip of fixed finger; dorsomesial margin not delimited; lateral and mesial surfaces with scattered granules; ventral surface weakly convex, nearly smooth. Fixed finger terminating in small corneous claw, with row of sharp calcareous teeth proximally and distal row of small corneous teeth. Carpus 3.0–3.2 times longer than wide, subequal in length to chela or merus; dorsolateral and dorsomesial margins rounded, each with row of stiff setae, dorsomesial margin with one small spine; dorsal surface nearly smooth; lateral surface divided into two sections (oblique dorsal and perpendicular ventral sections) by weak median ridge; mesial surface with scattered granules; ventral surface slightly convex. Merus nearly smooth on dorsal surface, dorsodistal margin unarmed; lateral face smooth to granular, ventrolateral margin with one small subdistal spine, otherwise smooth; mesial face nearly smooth, ventromesial margin without distinct spines. Ischium with smooth ventromesial margin; surfaces nearly smooth.

Left cheliped ( Figure 25D–F ) similar between male and female, elongate, slender. Chela about 3.2 times longer than broad. Dactylus longer than palm, with tufts of short setae on surfaces (setae on ventral surface longest); dorsal surface nearly smooth, dorsomesial margin not delimited; cutting edge terminating in small corneous claw, with row of small calcareous teeth in proximal 0.6 and with row of small corneous teeth in distal 0.4. Palm about half length of carpus; dorsal surface slightly elevated in midline and with few small granules and short setae, sloping mesial part with scattered small granules; dorsomesial margin not delimited; dorsolateral margin delimited by granular ridge; lateral surface with scattered small granules; mesial and ventral surfaces nearly smooth, latter with scattered tufts of setae. Carpus subcylindrical, 1.2 length of chela and subequal in length to merus; length 3.6–3.7 of distal width and about 4.0 of greatest height; dorsolateral and dorsomesial margins each weakly delimited by row of tubercles or granules and long stiff setae; lateral surface faintly divided into oblique dorsal and perpendicular ventral sections; mesial surface nearly smooth, with stiff setae dorsally and ventrodistally; ventral surface slightly convex, nearly smooth. Merus with low transverse ridges and stiff short to moderately long setae on dorsal surface, dorsodistal margin unarmed; lateral surface nearly smooth, ventrolateral margin with small distal spine, otherwise unarmed; mesial surface smooth, ventromesial margin unarmed; ventral surface weakly granular, with tufts of stiff setae. Ischium with smooth ventromesial margin; surfaces unarmed.

Ambulatory legs ( Figure 23C, E .) fairly long and slender, generally similar from right to left. Dactyli ( Figure 23D, F ) 0.7–0.8 length of propodi in second, 0.9–1.0 length in third, 8.0–9.0 times longer than high in second, 10.0–12.0 in third, nearly straight with weakly curved, strong corneous claws; dorsal surfaces each with sparse row of stiff setae; mesial surfaces unarmed (second), with few small corneous spinules dorsally or with row of five to nine small corneous spinules dorsally (third); ventral margins each with seven to 12 corneous spines notably increasing in size distally. Propodi slightly tapering distally, 4.9–5.5 times longer than high; dorsal surfaces each with low, short transverse ridges or protuberances and stiff setae (setae more numerous on third); lateral surfaces nearly smooth, with few short setae; ventral margins each with row of three to five corneous spinules, ventrodistal margins each with single or paired corneous spines. Carpi usually with small dorsodistal spines; dorsal surfaces each with low protuberances or short transverse ridges, and with stiff setae. Meri each with row of low protuberances or transverse ridges on dorsal surface, and with dorsal row of tufts of short stiff setae; lateral surfaces nearly smooth; ventrolateral distal margins each with small subdistal spine (second) or unarmed (third); ventral margins sinuous or slightly convex, with few setae.

Fourth pereopods ( Figure 23G ) similar. Dactyli terminating in small corneous claws, each with row of tufts of short setae on dorsal margin. Propodi each with nearly flat mesial face; rasp consisting of single row of corneous scales. Carpi moderately setose.

Anterior lobe of sixth thoracic sternite ( Figure 23H ) transversely oval or nearly subrectangular, anterolateral angles rounded; ventral surface with transverse row of stiff setae anteriorly. Eighth thoracic sternite ( Figure 23I ) composed of two slightly unequal, rather widely separated, rounded lobes.

Coxae of fifth pereopods ( Figure 23I ) slightly unequal in male. Right coxa with tuft of long stiff setae directed towards left and reaching to left coxa; posteromesial protrusion absent, no papilla-like sexual tube apparent. Left coxa with papilla-like protrusion of vas deferens, and tuft of short setae directed posteroventrally posterior to gonopore. Female with paired gonopores.

Telson ( Figure 23J ) with three to five small spines on each nearly horizontal terminal margin.

Colouration

In preservative. Shield entirely cream. Ocular peduncle cream, with tinge of red at base of cornea dorsally. Antennular peduncle generally cream, but distal half of ultimate segment dark reddish-brown. Antennal peduncle also generally cream, fifth segment with lateral red stripe; antennal flagella alternated with white and brown every three or four articles. Chelipeds generally cream; palm of right cheliped with tinge of reddish-brown on dorsal surface; merus of right cheliped also with reddish-brown blotch dorsodistally. Left cheliped with thin red longitudinal stripes; palm with three dorsal and one ventral stripes; carpus with stripes along dorsolateral and dorsomesial margins and two stripes on each lateral and mesial face; merus with one dorsal, three lateral, three mesial and two ventral stripes. Ambulatory legs also generally cream with red thin longitudinal stripes; dactyli each with three lateral and three mesial stripes; propodi each with three lateral and three mesial stripes, ventral surface not clearly striped but with tinge of red; carpi each with four lateral and four mesial stripes, ventralmost stripe sometimes obscure; meri each with dorsal and ventral surfaces bordered by lateral and mesial stripes, and with three lateral and two mesial stripes.

Distribution

Known from New Caledonia and Chesterfield Islands, 28–58 m.

Size

Largest male SL 4.9 mm, largest female SL 4.1 mm, ovigerous females SL 2.9–4.1 mm.

Etymology

From the Latin ruber meaning red and vittatus meaning striped, referring to the colouration of the chelipeds and ambulatory legs.

Remarks

The assignment of this new species to the presently recognized informal species groups is not easy. The ultimate segment of the antennular peduncle lacks ventral setal rows, and in this regard, P. rubrovittatus is referable to the P. anceps group. However, the ventral flagellum bears lateral and mesial rows of setae and numerous scattered setae on the ventral surface of the proximalmost article, suggesting the relationship to the P. boninensis group. Furthermore, the divided lateral surface of the carpus of the left cheliped and the tendency of elongation of chelipeds and ambulatory legs link the new species to certain species of the subgroup A of the P. boninensis (cf. Komai and Osawa 2006). Indeed, P. rubrovittatus closely resembles P. maorus both in morphology and colouration (cf. Komai and Asakura 1995; Komai and Osawa 2006). In particular, in both P. rubrovittatus and P. maorus , the male right cheliped can be extremely elongate; the chelipeds and ambulatory legs bear reddish-brown longitudinal stripes. Morphological differences other than the setation of the ultimate segment of the antennular peduncle include the armament of the chelipeds. In P. rubrovittatus , the carpus of the left cheliped does not have conspicuous spines on the dorsal surface, whereas in P. maorus , it is armed with dorsolateral and dorsomesial spines. The carpus of the female right cheliped in the new species bears only a single dorsomesial spine, which arises at midlength. In contrast, in females of P. maorus the carpus of the right cheliped has dorsolateral and dorsomesial rows of spines. In life, P. rubrovittatus is easily recognizable as having the striped pattern of colouration of the chelipeds and ambulatory legs and the possession of a dark distal ring on the ultimate segment of the antennular peduncle. In P. maorus , there is no ring on the antennular peduncle.

Figures

Figure 22. Pagurixus pilosus sp. nov. paratype, female (shield length 2.8 mm; MNHN-Pg 8322). (A) Right chela, dorsal view; (B) right cheliped, mesial view; (C) right cheliped, lateral view; (D) carpus of right cheliped, dorsal view. Note: Scale bar, 1 mm.

Figure 23. Pagurixus rubrovittatus sp. nov. holotype, male (shield length 4.4 mm; MNHN-Pg 8325. (A) Shield and cephalic appendages, dorsal view; (B) ultimate segment and ventral flagellum of left antennule, ventral view; (C) right second pereopod, lateral view; (D) right second pereopod, dactylus, mesial view; (E) right third pereopod, lateral view; (F) right third pereopod, dactylus, mesial view; (G) distal three segments of left fourth pereopod, lateral view; (H) sixth thoracic sternite, ventral view; (I) coxae of fifth pereopods and eighth thoracic sternite, ventral view; (J) telson, dorsal view. Notes: Scale bars, (A, C, E) 2 mm; (B, D, F, H–J) 1 mm; (G) 0.5 mm.

Figure 24. Pagurixus rubrovittatus sp. nov. holotype, male (shield length 4.4 mm; MNHN-Pg 8325. (A) Right chela, mesial view; (B) carpus and merus of right cheliped, mesial view; (C) right chela and carpus, lateral view; (D) merus of right cheliped, lateral view; (E) left cheliped, mesial view; (F) left cheliped, lateral view. Notes: Scale bars, (A–D) 2 mm; (E–F) 1 mm.

Figure 25. Pagurixus rubrovittatus sp. nov. (A–B, D–F) holotype, male (shield length [SL] 4.4 mm; MNHN-Pg 8325); (C) paratype, ovigerous female (SL 2.9 mm; MNHN-Pg 8330). (A) Right chela, dorsal view; (B) carpus of right cheliped, dorsal view; (C) left chela and carpus, dorsal view; (D) right chela and carpus, dorsal view; (E) right cheliped, mesial view; (F) right cheliped, lateral view. Notes: Scale bars, (A–B) 2 mm for; (C–F) 1 mm.